Simply extend at your nearest immigration office before the current stamps expiry date.
First with the "normal" 30 days.
After (if government still allows, we don't know yet*) apply for a 60day "Due to Covid" extension if you like to stay a tourist. All extensions cost same . . . 1900tbh
* Covid extension can be applied for till Sept 27, most likely they keep pushing this date forward as they (government) been doing since last year.
Your question is a bit irrelevant in the current situation.
Since where would you like to apply for a new tourist visa?
Return back to your home country?
In Thailand you can only get extensions at the moment. And with this you can stretch it quite far, as long as they are giving the "allowance of stay due to covid" 60 day extensions
For a new tourist visa you need to get out of the country, and currently it is not as the older days that you hop to Malaysia to get a new tourist visa.
Malaysia is closed, Thailand is not easy to get in .. and if you would get in you have to quarantine on both sides atm, or embassies are not even giving the visas out.
you can apply for another 60 days as long as the government allows. The application deadline atm is May 29. You be stamped back to back since it's your follow up (1st C-ext is from date of application).
Most immigration offices allow you to apply 30 days before expiry date of your current stamp (you will not "loose" days).
That is not how it should be. If you really entered on a 60 day Tourist visa (sticker in passport) you first are eligible for 30 days. Maybe because Pakistan passport is different agreement, I know Indian is (sorry I know not same country) or immigration made mistake.