You generally have to get the 30 day extension before they will grant the 60 day covid one, so you're going to have to just apply for the 30 day one. Very easy to do. Absolutely no need to use an agent. Anyone can do it themselves with almost zero effort. There's no speeding up the process as it is granted on the spot. Agents are only helpful because you don't have to go to immigration yourself.
You didn't come on a 30 day Thailand Pass. Thailand Passes are not visas and don't allow any particular length of stay. They are just a government approval of your entry documents to ensure you have the proper hotel booking, covid test bookings, insurance, etc. You still need whatever visa you needed to enter, or you likely entered on a 30 day visa exempt entry. The stamp in your passport is what shows your allowed stay-till date, not any length of time you originally put when you applied for Thailand Pass as your estimated stay length. If you go around asking about converting a Thailand Pass to a work permit, no one will understand what you are talking about. You need a Non-B visa and a work permit, not just a work permit. Work permits are issued by the Ministry of Labor, NOT by immigration so going there won't do a thing for you. And work permits are applied for by the employer, not by yourself. Both the Non-B visa application and work permit application process takes many steps with many documents and photos required. Here's the list for the Non-B:
This won't be clear until publication in the Royal Gazette. If like the previous changes, the rules that applied when you got approved will apply for your stay.
Regulations require that if Samui is your first destination in Thailand, your transit flight from Bangkok to Samui must be booked on the same through itinerary as your incoming international flight only on one of the special "Sealed Route" Bangkok Airways flight numbers which are always 4 digits beginning with "51".
The special designated "Sealed Route" flights are only for international arrivals, and are only bookable in conjunction with the international flight. This is to prevent mixing of international passengers (who have not yet had arrival covid tests) with the normal domestic passengers (who do not have such screening requirements) to prevent the risk of spreading Covid from the international travelers to domestic travelers.
The sealed route flights cannot be bought separately and can only be booked by your international airline carrier as part of your incoming single itinerary with your international flight. These special sealed route flights cannot be found for sale on the Bangkok Airways website, since they are not bookable by the public. If your flight number IS for sale on the Bangkok Airways website when you search flights, then it is a normal domestic flight and CANNOT be used for the sealed route. Any similar flight numbers do not count: for example, PG5171 is NOT the same as PG171 which also flies daily.