You should check how much insurance you need, how much funds in bank you need, you also need a medical check up for virus and certificate before travelling you will have to quarantine in a Registered hotel for 14 days. Check on Thai Embassy Bangkok website for all information
It is not uncommon for immigration to put wrong stamp or enter wrong information into computer.I had immigtation put my renentry stamp in my passport and did not put expiry date. Also when I applied for online 90 day checkin. The information in my passport did not match the information in the computer meaning info entered in computer was incorrect. I would just use the stamp in your passport if you are concerned go back and check with immigration.