@Yi ***********
Your extension of stay based on employment is valid no later then:
1. The date stamped in your passport, OR;
2. The date on your work permit, OR;
3. The last date you worked
Depending which date is first.
Legally, your extension of stay based on employment ended on the last day you worked, and you've been on amnesty since. You need to cancel your extension of stay based on employment and work permit, and go to your local immigration office and get an amnesty stamp for 1,900 THB. You should be able to stay in Thailand for an additional 60 days.