What are the best options for extending a DTV visa from Chiang Mai?

Mae Sai/Tachilek border is closed to non-Thais and non-Burmese.

If you use Chiang Saen border to cross to Laos by boat (Golden Triangle Special Economic Zone), you have to stay at least 1 night. 2000 baht entry for non-ASEAN citizens.

I would just do research of that area of Laos and you'll see why.

i used to ride a motorbike to the chiang khong border it takes about 4 hours to the border so you can leave in the morning and come back in the late afternoon

ChiangMaiVisaRun.com

TLDR: Use a border bounce agency for the simplest solution. Or take one of the busses that goes from Chiang Mai to Chiang Khong.

I've seen a recent report from Chiang Mai that they will not accept a foreign bank account, even though the official list of requirements states that a foreign bank account is okay. So it seems in general a border bounce is the way to go.

From Chiang Mai you have the option of international flight out and back.

I believe there are also busses from Chiang Mai that go directly to Chiang Khong, which is going to be where border bouncers go. I'm not sure on the logistics of timing for leaving and returning, what the bus timetables are though. You shouldn't have issues at the Chiang Khong border with a visa, it's only people without a visa that are subject to the 2 nights in Laos based on recent reports.

You also have the option of using a border bounce agency in Chiang Mai if you don't want to worry about the logistics at all. They'll drive you to Chiang Khong and back in a single day.

If you wanted to drive it yourself on a motorcycle, you're look at 5+ hours each way. It's possible, but you had better feel up for it. There's some pretty nice views up around that area, as I've driven from Chiang Rai to Chiang Khong on motorcycle before. You could spend a night in Chiang Rai if you want to split up the trip.