Regardless of what the MFA says there is still no clarity regarding in country extensions. No one knows the requirements or cost. There has been recent chatter that the Immigration Office will refuse in country extensions. It’s all unclear at this time.
Most agents aren’t interested unless you’re physically in Thailand and looking to immediately sign a lease. Pet friendly will indeed be a difficult search.
correct you will not pay twice but that does not mean you don’t have to pay anything. If the tax rate is higher in Thailand you will be required to pay the difference so you could be taxed in your home country AND taxed in Thailand.