Is having a probation period and applying before my first salary okay for a DTV in Thailand?

Probation does not block DTV approval. Thai embassy checks that your job is genuine and remote. If your offer letter shows company name outside Thailand, your role, salary and start date two November, and contract mentions probation six months, that is normal. Probation is standard in many companies so they accept it.

For salary part, you can apply before first salary if your bank balance meets requirement. Indian applicants usually need six months statement with good closing balance around five lakh baht equivalent. If you have three months savings only, add your previous job payslips and explain in cover letter that new job starts soon. That makes file stronger.

Many Indian files with new job offer and probation were approved after showing offer plus bank plus company profile. I found a clear example for this exact case in Unlock Thailand by Isla Rey on Amazon, it shows what letter and bank combo works for new job DTV. Worth checking for your timeline.

You have a risk getting rejected with a contract with probation.

Salary slips are not always asked, but when they do ask and you don't have them you might have a problem.

Only embassy can tell you for sure.

You can include previous employment documents and explain your transition in a cover letter.