Please do not MIX different things.

There is a Visa which you obtain before you make your way into Thailand at a Thai Embassy or on-line,

There is a conversion of a Visa Exempt Entry or Tourist Visa at a local Immigration Office after you entered Thailand

And there is:

an Extension of Stay for which you apply at the end of the period of stay you got when you entered Thailand.

Different things, different rules, regulations and requirements.

Correction:

1) Chang Wattana Immigration Office for the Extension of Stay based on a tourist visa.

2) On line, after you registerd using the website

Or Muang Thong Thani if you go in person.

@Darren ******

Good guess, the employer can cancel the work permit but not the Extension of Stay as the passport is needed to cancel the stamps.

TM 8 for those who are not familair with form numbers:

Application form for the Re-Entry Permit.

It does not matter if dates changes from written to actual flying out. The permit is valid as long as your current Permitted to Stay period.

If you leave and having a re-entry permit, you will get the same Admitted until date as you have now as permitted up to, in your case 28th May 2022. You need to apply before that date for a new 1 year Extension of Stay.

How did you proved your income last year?

If banked money, you have to proof that you kept your promisses.

I guess that you do not have a visa.

I guess you have a big stamp with the text:

Extension of Stay permitted up to 28.05.2022?

@Owen *****************

You can also cancel your work permit in advance.

Let's say two weeks before you stop working, go to Ministry of Labor in the morning, cancel your Work Permit with last day xx/xx/xx, have lunch, go Immigration and cancel Extension of Stay with last day xx/xx/xx,

To avoid, go in advance like twee weeks before you stop working.

@Ryan *******

You acknowledge to understand the rules, all the rules are not mentioned in that document but in the Immigration Law.

Next time ask before you sign.

It does not take 25 days to apply for a visa.

There is no official limit on how many Visa Exempt Entries a person can use in one year or in one life time.

The 30 day Visa Exempt Entry (not a visa) can be extended once with another 30 days based on tourism.

For Covid test prior arrival and after arrival you have to look at the page

as that is not Thai Visa related.