I can't speak to recent approvals, but the Royal Thai Embassy in Singapore only grants the DTV to Singapore citizens and Singapore permanent residents. Citizens upload both sides of the Pink IC; PRs upload both sides of the Blue IC and the Re-entry Permit (Form 7). So if you're on a work pass but not a PR, you'd need to apply elsewhere.
For Muay Thai, a letter from the camp to the Board of Boxing Sport confirming your training, plus the camp's letter from the Sports Authority of Thailand and Ministry of Tourism and Sports. For cooking, an enrolment letter from the school, plus its school license, business license or an affidavit. Funds: 3-month Singapore or Thailand savings statements of at least 500,000 THB (about 20,000 SGD); investment and CPF accounts aren't accepted. The fee is 500 SGD, non-refundable, for a 5-year multiple-entry visa.
Official:
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