Can I stay 60 days with an extension, fly to Penang for a week or 2, then return to BKK for another 30 + 30 extension?

Yes. 

What is your recent history of staying in Thailand.

 

 

I've never been before.

44 minutes ago, tjraveler said:

I've never been before.

You will have zero problems with your planned four month stay. However, recognise that you cannot rinse and repeat indefinitely.

If you apply for a 60 day TR visa you can also extend that for 30 day, then fly out and come back visa exempt for 30 + 30 if you want a bit more time.  Just need to apply for a TR visa on the front end

If you would like Abit longer stay for roughly the same cost, I suggest to visit Thai consulate nearby to you.

 

1. Apply 60-day TR60 visa.

2. Arrive Thailand, and go wherever you want for 60 days.

3. Day 59 or earlier, visit immigration and get a 30-day extension.

 

That will give you 90 days total without leaving the country.  If you exit t9 Penang/KL,  you can repeat this one more time(visit Thai consulate there and get TR60 once more ).   OR...just fly back in as Visa Exempt, and you will do 30+30.

Thanks for the help everyone.

45 minutes ago, tjraveler said:

Thanks for the help everyone.

OP, regarding you flying to Penang for week + ....

If you wish to go there yes that's an option.

Keep in mind that to obtain the visa exempt entry 30 + 30 with extention you can do that same same day with land border bounce.