One thing people want to do when arriving is to set up their phone and internet. There are three main phone companies in Thailand DTAC, AIS and TRUE. They are all the same and offer a variety of plans based on whether the internet or calls are more important for you. Thai people don’t call as much as western people and rely on messaging apps such as Line or Facebook Messenger. For around 300 baht a month you can get a package with a decent amount of internet data and a hundred or so minutes of call time.
Home internet is more dependent on where you live and the services offered in the region. Most internet companies try to sell you an internet and TV package. It works out at around 800 baht a month but this will include a few English channels. The internet speeds are increasing and for your 799 baht a month you should expect at least 50 MB connection speeds, simple TV package, and phone internet for 4 GB.
If TV is your thing then prepare to pay what you would back home to get movies and live premium TV (sports, western channels, etc). If English Premier League football is a must for you then TRUE now have exclusive rights so you must go through them, if it isn’t then AIS has some useful packages and sole rights to show HBO ( Game of Th, ones, etc). Premium tv and internet bundles cost up to 3,000 baht a month so it isn’t the cheapest way.
You can also get Netflix Thailand. It stars around 250 baht a month up to 440 baht for the 4K version.
I use this instead of expensive cable TV choices. I go to the pub if there’s a sports event I want to see.