Siem Reap

Agree with the people below plus would say Cambodia and Siem Reap are wonderful places to visit if you like super friendly locals, amazing food and an easygoing lifestyle.
There are a bunch of expats here, and a lot them are involved in social projects. If you're looking to do something good beyond experiencing a country, it's a good place to start.
WiFi is totally usable everywhere. Mobile data is cheap and fast.
Siem Reap has tons of options for food and drinks. It's very easy to get around or foot/bike now because they built a new, fit for purpose road with a CYCLE LANE all along the river.
I disagree that's there's not much to do - there's plenty in and around the city. The circus for me is a must-see. Angkor Wat is obviously amazing - take a bicycle because you get more out of it. Definitely go and see Apopo - they train rats to find landmines and it's such a good initiative. I liked the lotus farm too.

Places to stay - would recommend the Bygone. You could easily live there for a month. The owners are super chilled and friendly. They're also using the business to support charity so totally worthwhile.

I like Siem Reap, I like Cambodia. The whole city here has a "Large Village" feel. Wi-Fi here is pretty decent and a lot more stable than other places in the region I have tried, meaning connections won't always randomly drop. The whole country of Cambodia feels like it's a country heading in the right direction. I walk around, I see shops and eateries that have actual local Cambodian/Khmer people inside them enjoying them. I walk around, yeah, I'm getting random solicits for a ride but no one is overly pushy, "no" is accepted as an answer for the first time. It's manageable and I am not having things shoved in my face every 5 minutes pressured to buy stuff. I can walk and relax and not be so guarded. I also when I sit down at a place, notably pub street, workers here don't appear desperate or anxious, they all seem relaxed and when not serving people are visibly joking and smiling.

Even in a western facing area like pub street, locals are in the bars and restaurants and every place is owned by a local, makes me feel like money I spend here is being used to improve the local's every day living.

A week even seems a little much as after a few temples, having a night on Pub Street, and Angkor Wat being the highlight of any trip here, Siem Reap doesn't have much to see otherwise. It's a nice village feel, locals seem pretty relaxed and chill, which is fine for chilling and working for a week, maybe two if I really don't feel like doing much and staying in. I'd love to come back to Cambodia and see their capitol city of Phnom Penh at a later date.

Siem Riep has a nice suburb feeling. At first sight it seems there's not much to do besides Angkor Wat and Pub Street, but you can go swimming, do bicycle tours, floating village day trip...

I don't have best social skill, but in Siem Reap it was so easy to make new friends. Locals and tourists!

I've worked at Garage Society Coworking Space. Pretty nice place.

I don't understand the cons of slow internet. I've bought an LTE 4G Sim card for 10 USD with 10 GB. There's also free and mostly fast wifi at almost every cafe, restaurant, bar and hotel.

And about cost of lining: I've met some locals. First local was a single mom with 3 kids living 10 minutes away from pub street by tuk tuk. She is spending only 100 USD for 1 room studio apartment including water and power and 50 USD for food for her and the kids (I've been at her home). Second local was another girl who earned 120 USD per month by working at a hotel. So 400 USD cost of living for a local is waaay too high as it is mentioned here.

And night life is pretty awesome (at least it was before Covid 19). Bars and clubs everywhere at pub street and really crowded every night in high seasons. Temple Bar was awesome.