Everywhere is said that the DVR-027 is bets value for $60 money.

https://www.google.com/search?q=dvr-027

Where to buy in Thailand ?

I have had two of these. Neither lasted longer than 6 months but then again less than 1000 bht on eBay.

Next dash cam I want better quality.

Seen them for 800bht in Pantip or 1500bht at Tesco Lotus.

If one buys a dashcam that has a cig-plug adapter to plug into cig-lighter, how difficult is it to change the power source and connect it to the car battery?

What would be needed to do so?

Just cut the wires at the cig lighter, bare the wire ends. Connect the 'live wire' to any 'switched' supply. Connect the other wire to any bit of metal work. You may need a longer wire so in that case extend it .. you will need a bit of tape to cover the join.

Of course you could connect the wires direct to the car battery ... good idea to put a fuse in line though ... in the + side!

If it hasn't been mentioned already, check out Techmoan on youtube. He does the best reviews for dash and action cams.

If one buys a dashcam that has a cig-plug adapter to plug into cig-lighter, how difficult is it to change the power source and connect it to the car battery?

What would be needed to do so?

Just cut the wires at the cig lighter, bare the wire ends. Connect the 'live wire' to any 'switched' supply. Connect the other wire to any bit of metal work. You may need a longer wire so in that case extend it .. you will need a bit of tape to cover the join.

Of course you could connect the wires direct to the car battery ... good idea to put a fuse in line though ... in the + side!

Do not do that

If you look at the cig-plug you will find that it reduces the voltage for the camera - usually 5v.

If you need to extend the wire get one of those multi cig-pug extension things that you can wire to the battery and pug the camera into that.

Or if you feel confident remove the cig-plug casing on the camera lead and extend the wiring being sure to leave the voltage reducer in-line.