| Season: | 1998 |
| Dates: | 2 May – 3 October |
| League Topscorer: |  Ronnachai Sayomchai (Port Authority of Thailand) (23) |
| Nextseason: | 1999 |
The 1998 Thai Premier League consisted of 12 teams. The bottom club would be relegated to the Thailand Division 1 League. The club that came 11th would play in a relegation / promotion match against the club that came second in the Thailand Division 1 League
Defending Champions Royal Thai Air Force should have entered the next edition of the Asian Club Championship, but refused due to lack of funding. BEC Tero Sasana took their place.
The league was also known as the Caltex Premier League.
The club that came 11th would play in a relegation / promotion match against the runner-up in the Thailand Division 1 League.
January 24 and January 31, 1998
† Bangkok Metropolitan Administration remain at the Thai Premier League.
The Singha sponsored Queen's Cup was postponed because of lack of sponsorship, will be held next year but with reduced prize money.
Bangkok Bank won the 1998 Thailand FA Cup, and their 3rd victory in this competition. It is unclear whom they beat in the final
1998 saw the 14th edition of the Yamaha Thailand Cup.
It was Thailand's main inter-provincial competition, played between qualifiers from various regions.
The first round saw four groups of four teams, of which the top two sides qualified for the Quarter-Final knockout stage.
Bangkok Metropolitan Administration beat Nakhon Si Thammarat in the final.
Karoon Narksawat - Sinthana Ronnachai Sayomchai - 23 Goals[1] Port Authority of ThailandThe champion for the 1998 season was Sinthana. It was the team's first title.