Proposal to change certain Thai translations in Locale

Hello! I'm a native Thai speaker who happened to stumble upon your project. I would love to propose the following changes as detailed in the comments.

```python
past = "{0} ที่ผ่านมา" # --> The present translation is fine, but it sounds more natural to use ที่แล้ว.
# For example, if I use this library to print out the last check point, ที่แล้ว is more suitable

timeframes = {
"now": "ขณะนี้",
"second": "วินาที", # --> this should be changed to "1 วินาที"
"seconds": "{0} ไม่กี่วินาที", # --> this should be changed to "{0} วินาที"
"minute": "1 นาที",
"minutes": "{0} นาที",
"hour": "1 ชั่วโมง",
"hours": "{0} ชั่วโมง",
"day": "1 วัน",
"days": "{0} วัน",
"month": "1 เดือน",
"months": "{0} เดือน",
"year": "1 ปี",
"years": "{0} ปี",
}
```
I'm happy to make these minor changes if you see fit and submit a pull request. I also saw that you are looking to improve test cases in various languages. I am happy to write some tests for Thai, but I need a bit more time to familiarize myself with the library. I'm fairly new to open source contribution as well, but would love to learn and do more.

Start by locating the Thai Locale entry corresponding to the Python translation block and read the two issue comments for the full context. If adding tests, inspect the existing language test cases; done means the listed Thai strings match the agreed translations and relevant tests pass.

Written by the indexing model from the issue text.