Sorry this is basically a yes no answer question.
Just got new passport and also due to do first 90 day reporting at immigration.
Should I do 90 day reporting before or after I get them to transfer my visa stamps into new passport?
In an ideal world like to do it all in 1 visit (Jomtien). Then forget old passport.
TLDR : Answer Summary
When handling your 90-day reporting and transferring visa stamps to a new passport in Thailand, it's generally advisable to transfer the visa stamps into the new passport first and then complete the 90-day reporting. However, some users have noted that both tasks can be done in a single visit, with the important detail being to ensure the new passport number is in the system for the reporting. Always bring both passports and any necessary documents, such as a letter from your embassy regarding your visa.