| Post: | Crown Prince |
| Body: | Thailand |
| Native Name: | สยามมกุฎราชกุมาร |
| Insignia: | Crown Prince's Standard of Thailand.svg |
| Insigniacaption: | Standard of the Crown Prince |
| Incumbent: | Vacant |
| Incumbentsince: | 13 October 2016 |
| Style: | His Royal Highness |
| Type: | Heir apparent |
| Appointer: | Monarch |
| Termlength: | Life tenure or until accession as Sovereign |
| Precursor: | Viceroy of Siam |
| Inaugural: | Vajirunhis |
The Crown Prince of Thailand (or Siam; Thai: สยามมกุฎราชกุมาร; ; lit. the royal son of Siam) is a title held by the heir apparent to the Thai throne. First created by King Chulalongkorn (Rama V) in 1886, for his son Prince Maha Vajirunhis, the king's eldest son by a royal wife Queen Savang Vadhana. Prior to this, the Siamese throne did not have a law or formal system regulating the royal succession. In 1688 King Phetracha of Ayutthaya created the title of Front Palace, which by the Rattanakosin period had become the main title granted to the heir presumptive to the throne. However few Front Palaces have succeeded to the throne this way, with the exception of King Phutthaloetla Naphalai (Rama II) in 1809. After the death of Bowon Wichaichan in 1885, the title of Front Palace was abolished and replaced with the title of Crown Prince, who became heir apparent to the throne.
In 1924 King Vajiravudh (Rama VI) promulgated the 1924 Palace Law of Succession to regulate the succession, this law essentially barred females, children of commoner wives or children of foreign wives to the throne, it also re-affirmed agnatic primogeniture, or succession through the male-line by seniority. This law also affected the individuals who could become Crown Prince. Since its creation three Princes have been raised to this title, and two have succeeded to the throne.
The title in Thai, Sayammakutratchakuman, comes from conjugation of the words Sayam (Siam), Sanskrit makut (meaning “crown”), ratcha from Sanskrit rāj, and kuman from Sanskrit kumār (meaning “son”).
| Picture | Name | Relationship to monarch | Mother | Birth | Receive title | Ceased to be Crown Prince |
|---|---|---|---|---|---|---|
| Maha Vajirunhis | Eldest son with queens of King Rama V | Queen Savang Vadhana | 27 June 1878 | 14 January 1886[1] | 4 January 1895 (death) | |
| Maha Vajiravudh (later King Rama VI) | Third son with queens of King Rama V | Queen Saovabha Phongsri | 1 January 1881 | 4 January 1895[2] | 23 October 1910 (ascension) | |
| Maha Vajiralongkorn (later King Rama X) | Only son of King Rama IX | Queen Sirikit | 28 July 1952 | 28 December 1972[3] | 13 October 2016 (ascension)[4] | |
List of heirs apparent and heirs presumptive since 1886, those in bold succeeded to the throne as King.
| Heirs to the Thai Throne | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Heir | Status | Relationship to monarch | Became Heir | Ceased to be Heir | Next in line of succession (Relation to heir) | Monarch | |||
| Date | Reason | Date | Reason | ||||||
Crown Prince Maha Vajirunhis | Heir apparent | Eldest son with queens | 14 January 1886 | New creation | 4 January 1895 | Died of typhoid | Prince Vajiravudh, Prince of Ayutthaya 1886–1895, younger half-brother | Rama V | |
Crown Prince Maha Vajiravudh | Heir apparent | Third son with queens | 4 January 1895 | Elder half-brother died | 23 October 1910 | Father died; became king | Prince Chakrabongse Bhuvanath, Prince of Phitsanulok 1895–1910, younger brother | ||
Prince Chakrabongse Bhuvanath, Prince of Phitsanulok | Heir presumptive | Younger brother | 23 October 1910 | Elder brother became king | 13 June 1920 | Died of pneumonia | Prince Asdang Dejavudh, Prince of Nakhon Ratchasima 1910–1920, younger brother | Rama VI | |
Prince Asdang Dejavudh, Prince of Nakhon Ratchasima | Heir presumptive | Younger brother | 13 June 1920 | Elder brother died | 9 February 1924 | Died of nephrosis | Prince Chudadhuj Dharadilok, Prince of Phetchabun 1910–1923, younger brother | ||
| Prince Varananda Dhavaj Chudadhuj 1923–1924, nephew | |||||||||
Prince Varananda Dhavaj Chudadhuj | Heir presumptive | Nephew | 9 February 1924 | Uncle died | 2 September 1924 | Skipped by the royal command[5] | Prince Prajadhipok Sakdidej, Prince of Sukhothai 1924, uncle | ||
Prince Prajadhipok Sakdidej, Prince of Sukhothai | Heir presumptive | Younger brother | 2 September 1924 | Nephew was skipped | 25 November 1925 | Elder brother died; became king | Prince Mahidol Adulyadej, Prince of Songkla 1924–1925, elder half-brother | ||
Prince Mahidol Adulyadej, Prince of Songkla | Heir presumptive | Elder half-brother | 25 November 1925 | Younger half-brother became King | 24 September 1929 | Died of pneumonia | Prince Ananda Mahidol 1925–1929, eldest son | Rama VII | |
Prince Ananda Mahidol | Heir presumptive | Half-nephew | 24 September 1929 | Father died | 2 March 1935 | Abdication of half-uncle; became king | Prince Bhumibol Adulyadej 1929–1935, younger brother | ||
Prince Bhumibol Adulyadej | Heir presumptive | Younger brother | 2 March 1935 | Elder brother became King | 9 June 1946 | Elder brother died; became King | Prince Paribatra Sukhumbandhu, Prince of Nakhon Sawan 1935–1944, half-uncle | Rama VIII | |
| Prince Chumbhotbongs Paribatra 1944–1946, half-first cousin | |||||||||
Prince Chumbhotbongs Paribatra, Prince of Nakhon Sawan II | Heir presumptive | Half-first cousin | 9 June 1946 | Half-first cousin became king | 28 July 1952 | Son born to king | Prince Sukhumabhinanda 1946–1952, half-brother | Rama IX | |
Crown Prince Maha Vajiralongkorn | Heir apparent | Only Son | 28 July 1952 | Born | 13 October 2016 | Father died; became King | Prince Chumbhotbongs Paribatra, Prince of Nakhon Sawan II 1952–1959, half-first cousin once removed | ||
| Prince Sukhumabhinanda 1959–1974, half-first cousin once removed | |||||||||
| Princess Maha Chakri Sirindhorn, Princess Royal 1974–1978, younger sister | |||||||||
| Princess Bajrakitiyabha 1978–1979, only daughter | |||||||||
| Prince Juthavachara Mahidol 1979–1997, eldest son | |||||||||
| Princess Bajrakitiyabha 1997–2005, eldest daughter | |||||||||
| Prince Dipangkorn Rasmijoti 2005–2016, only recognised son | |||||||||
Prince Dipangkorn Rasmijoti | Heir presumptive | Only recognised son | 13 October 2016 | Father became king | Princess Bajrakitiyabha, Princess Rajasarini Siribajra 2016–present, elder half-sister | Rama X | |||