What kind of age are you Bill? If early 50s you can get one years health insurance for the o-a visa for about $500 (with quite a hefty excess if you actually want to use it) but the older your are the heftier the premium is
If you're still resident in UK then even with Polish passport you can apply for an e-visa. If you're back in Poland then it will be the old fashioned way
Assuming, as you're from Hong Kong, you have a Hong Kong passport in which case you arrived visa exempt, not visa on arrival. You would have been stamped in for 30 days and that can be extended once by another 30 days at any immigration office for a fee of 1900 baht