Frankly I believe that you are at great risk of being questioned by Thai Immigration Officers upon arrival from Singapore and possible DENIED entry.
If you have the 30 day extension available to you from your local Thai Immigration office, get it...
AND buy a single reentry permit...
Which will grant you entry on your return from Singapore with a STAMPED ending date same as the 30 days extension you obtained.
Or...
Contact a Fast Track Service Company to ASK them if they accept you for Fast Track Service upon your arrival from Singapore.
You will get a NEW 60 day stamp as Visa Exempt Entry.
Tell them your passport nation, recent history of entries into Thailand, whether you have been DENIED entry before or are on ok OVERSTAY.
Here's the largest BORDER BOUNCE service company which also offers Fast Track Service in Phuket, oth airports in Bangkok and the Chiang Mai Airport.
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