Ban Bueng Devil Rays had stunned the reigning champions 86-73 in the first match on Saturday in the best-of-three finals.
Thung Khru Hi-Tech fought back to tie scores, winning the second match 84-69.
The decider to determine this year’s champions will be played on Wednesday at 4pm at Nimibutr Building in Bangkok.
The 2022 Thailand Basketball League, organised by the Thai Basketball Professional Association, began on June 25 and ends on August 24. Ten teams were in the fray for a total prize money of 4 million baht.
The winner will also get a slot in the 2022 FIBA Asia Champions Cup at the end of this year.