I stay in a condo and they do it for me for 100 baht or something.. You can do it yourself if you want. I choose to do it regardless if it's necessary or not. It doesn't hurt anything and costs next to nothing.
AirBnB often have some sort of "cooking area" with limited cooking supplies.
An induction cooker (Hot plate) is pretty cheap. I have dietary restrictions also and when I travel to exotic places I tend to stick with fruits and vegetables.
You could apply for a visa now for your January trip. You have to use it when doing border bounces.
I have been in Thailand nearly ten years and most of that time was tourist visas. I have been pulled aside by immigration twice. They yelled at me, then let me in. You will likely be fine but you are assume certain risks.
You can easily stay 6 months with visa exempt and a border run. You're here to see the sights anyway.
Pattaya city proper may be a little much unless you are into partying
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. Otherwise I would recommend the outskirts. Pattaya is nice enough, I live here now and have been here 5 years. However, Pattaya is in Thailand, it's not really Thailand. Its a town of tourists or expats who like to party. If you want to see real Thailand, I would recommend planning 1 week here and another week there, etc. It may be more expensive but it's a once in a lifetime experience.. Unless you end up living here.