Let me post you the official answer from the Thai Embassy in Singapore + MFA.
“Not required (for stay not exceeding 30 days for each entry and a cumulative duration of stay not exceeding 90 days within any six months).“
Main Pt: you cannot accumulate >90days stay in TH over rolling 6 month period.
https://www.mfa.gov.sg/Overseas-Miss...20six%20months).
https://singapore.thaiembassy.org/en...f57a70d05b3143
https://image.mfa.go.th/mfa/0/GuK2Xa...April_2023.pdf