Does uploading a torrent influence in any way the speed of a computer ?

Yes, if you are trying to "surf" the web, downloading a torrent can have a major effect on how fast your pages refresh

If your are "seeding" a torrent that may also have an effect on your browsing, unfortunately I have never uploaded a torrent so I can't answer that one

Does uploading a torrent influence in any way the speed of a computer ?

it will affect the speed of any task of your computer for the simple reason that your main processor has to share its capacity.

Unlikely to have a noticeable effect on your computer's speed as once it's finished hashing the required CPU power is small.

It will however have a slight detriment on browsing if the upload is filling your up pipe, throttle to 80% of your max up speed and you'll see little effect.

On most modern computers the processing speed required will make the performance drop unnoticeable. However, you are using your 'upload' bandwidth, which on most subscriber lines is far lower in capacity then your 'download' bandwidth.

You have to be careful to tone down your upload speed (you can set that in your client), as to not to drown out your other traffic. You can experience very slow internet browsing speeds, even with your download bandwidth mostly unused, because your requests are queued up behind your torrent (which can behave quite aggressively).

It's best to keep your seeding / upload speed below 80% of your currently supported upload bandwidth (this is NOT the advertised speed of your line, first do a speed test to see how much you really get, and take 80% of that as a starting point. Lower it when you still notice internet slowdowns)

Uploading can have a big effect on browsing as your upload is normally a lot less speed than download. When you are uploading it takes a big chunk out of the download speed something like 512 up would wipe out a 1500 downstream.

Unlikely to have a noticeable effect on your computer's speed as once it's finished hashing the required CPU power is small.

It will however have a slight detriment on browsing if the upload is filling your up pipe, throttle to 80% of your max up speed and you'll see little effect.

It can be quite a significant effect on browsing. Uploading a torrent is very efficient in that it will fill your entire upload bandwidth if you don't limit it. You might think "but I am not uploading anything else" but that's wrong - example when you go to a web page, you need to first send a request to that server. It's a small amount of data for the request, but it's going up, and if your upload is totally saturated by seeding a torrent you'll have trouble getting through sometimes. Each page request creates hundreds of server requests. Similar for mail, and even downloading a torrent.

So it's important to limit your upload speed. 80% of line capacity is a good idea.

The uploading speed in Thailand is not very high. So it will have no affect on your internet speed.