I want to fit one of those isolating switches between the meter and the CU. I was thinking of locating it inside an IP45 box on the front of the house so that it isn't easily swictched off/on by, say, an unwanted intruder, or a well intentioned local while your working on the CU). I guess the downside is that it couldn't easily be switched off in case of emergency (you'd have to unscrew the 4 plastic screws to open the box) but is there any reason other reason why this might not be a good idea ? Thanks.

is there any reason other reason why this might not be a good idea ?

Why would you want a switch outside and don't you have a switch on the CU.

Isn't it a good idea to have a utility isolator between the meter and the consumer unit/distribution board ?

UK supply companies are now recommending an isolator after the meter, expect it to become a legal requirement eventually.

The big advantage is that you can pull that breaker and know all of your internal system is dead. I'm not a great lover of poking around in a CU knowing that at least one terminal is still live, and of course without an isolator replacing a CU requires one to (illegally) pull the supply fuse (which we don't have in Thailand anyway).

If that is your only reasoning put it next to the CU, needs no IP rated box then.

If you also want it as emergency isolation (a Fireman's Switch) then it needs to be readily accessible. A lockable IP65 box would do the trick, easy enough to open without a key in an emergency, but hard enough to prevent 'helpful' persons turning it off (or on).

PEA may let you put it on their pole, but of course it's accessible by all and sundry.

The main switch should be on or adjacent to the main switch board. In Thailand this should be a 60 or 63A MCB rated at 10kA at 220V.

eg. a Square D MCB.