What I wrote above with the 180 days was not quite correct. sorry about this. What I meant is the tourist visa 60 days (multiple entries) and that can be extended 2 times by exit and re-entry to 180 days plus 3 times 30 days extension in Thailand directly. So a total of 270 days.
I'm not exactly sure, but I think there is no limit. But what I do know is if you're constantly coming in on a tourist visa, they may check you out to see if you're not working in Thailand. What you are not allowed to do with a tourist visa.
If he has to renew his visa every 12 months, then he has a long-stay visa and not a tourist visa. So he must have
*****
0 baht in an account or
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0 baht if he is married to a Thai. You can extend a normal tourist visa 2 times, i.e. max. 180 days in Thailand. And as has already been said, each extension costs 1900 baht. No matter which visa or entry stamp.
Here in Germany you can get the Test Result same day, price is 39€ and if you can wait until first of June, you upload and you get immediately your QR Code
I am 99% sure there has never been a ferry from Phi Phi Island to Kradan. Currently there are almost no ferries from Phuket, only the most important connections such as Phi Phi or Krabi. From Krabi you would have to get a speedboat connection to Kradan.