| Official Name: | Mae Sai |
| Native Name: | แม่สาย |
| Native Name Lang: | th |
| Settlement Type: | District |
| Pushpin Map: | Thailand |
| Pushpin Map Caption: | Location in Thailand |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Chiang Rai |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Mae Sai |
| Subdivision Type3: | Subdistrict |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 86,298 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 57130 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 5709 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 20.4281°N 99.8836°W |
Mae Sai (Thai: แม่สาย, in Thai pronounced as /mɛ̂ː sǎːj/; Shan:, in Shan pronounced as /mɛ.sʰǎj/) is the northernmost district (amphoe) of Chiang Rai province in northern Thailand. The town of Mae Sai is a major border crossing between Thailand and Myanmar. Asian Highway Network AH2 (Thailand Route 1 or Phahonyothin Road) crosses the Mae Sai River to the town Tachileik in Myanmar.
One-day passes for non-Burmese nationals crossing into Myanmar are issued at Myanmar customs in Tachileik. Passports are confiscated and a temporary travel permit is issued; the permit is exchanged for the traveler's passport upon crossing back into Thailand. (No longer available as of 2016.) Since the changes in Thai immigration policy since March 2016, crossing this border as a foreign national is highly depended on individual Thai customs officers, as they have discretion.
Mae Sai is north of Chiang Mai, north of Chiang Rai, and north of Bangkok.
Neighboring districts are (from the east clockwise): Chiang Saen, Mae Chan, and Mae Fa Luang. To the north is Myanmar, separated by the Mae Sai River and the Ruak River. The westernmost part of the district is dominated by the hills of the Daen Lao Range, the most important one is the Doi Tung with the Wat Phra That Doi Tung temple on top. Doi Nang Non is another notable mountain in Mae Sai District.
The minor district (king amphoe) Mae Sai was created on 1 March 1939, when the two tambons Mae Sai and Pong Pha were split off from Chiang Saen District.[1] The area was upgraded to a full district on 1 May 1950.[2]
The district is divided into eight subdistricts (tambons), which in turn are further subdivided into 92 villages (mubans). There are two subdistrict municipalities (thesaban tambons) in the district: Mai Sai itself covering parts of the tambons Mae Sai and Wiang Phang Kham, and Huai Khrai covering parts of tambon Huai Khrai. There are a further eight tambon administrative organizations (TAO).
| No. | Name | Thai name | Villages | Pop. | ||
|---|---|---|---|---|---|---|
| 1. | Mae Sai | แม่สาย | 14 | 21,697 | ||
| 2. | Huai Khrai | ห้วยไคร้ | 11 | 7,609 | ||
| 3. | Ko Chang | เกาะช้าง | 13 | 9,964 | ||
| 4. | Pong Pha | โป่งผา | 12 | 8,348 | ||
| 5. | Si Mueang Chum | ศรีเมืองชุม | 9 | 5,090 | ||
| 6. | Wiang Phang Kham | เวียงพางคำ | 13 | 19,945 | ||
| 8. | Ban Dai | บ้านด้าย | 8 | 4,117 | ||
| 9. | Pong Ngam | โป่งงาม | 12 | 9,528 |