Are most of the taxi drivers Thai? I was just wondering if many of them spoke other languages such as Chinese and what about English?

I don't think I've ever come across a taxi driver in Bangkok who wasn't Thai. Most of them can understand very basic English.

Most of taxi drivers I have used in Thailand spoke passable English and they always want to talk a little to practice. Now the ones that drive the motorcycle taxis and taxi trucks (pickup trucks with bench seating in the bed) are a whole other breed.

Taxi drivers in Bangkok speak basic English. That being said, certain names like hotel name or dept store name is pronounced very differently. It is always a good idea to have someone write the destination in Thai.

As I don't speak fluent Chinese, I didn't try them, but I doubt they would speak Chinese.

Do they still have the I love Farang stickers on some cabs?

You'll occasionally run into Thais (of Chinese descent) who can speak eg. Cantonese or Hokkien, but practically nobody speaks Mandarin.

Yes.
But the fact that you see those stickers on taxi windows is a sure indication that many here don't love foreigners very much.

The "I love NY" signs started appearing when New York started having serious problems.

-- Peter

No, most of the taxi drivers (in Bangkok) are not ethnic Thai, they are Lao-Isaarn.
Their language is Lao-Isaarn, not central Thai.

You do find a few ethnic Thais driving taxis in Bangkok, but not many.
In my experience, based on simple conversations, less than 5% are speaking central Thai.
I often ask the drivers what province they are from.
In two-plus years of riding in hundreds of taxis, only one has said he is from Bangkok.
Perhaps three or four have named provinces in central Thailand, and another few in the Northern provinces.
All the rest are from provinces in the Lao-Isaarn region.

I don't know about Chinese language, but some taxi drivers here have a smattering of Japanese.
I know because a few have practiced their Japanese language on me.
Why, I have no idea.

The problem with their English, is the Thai pronunciation of English words is very far from anything we would expect.
They add in their own tones and their own styles of vowel lengths and emphasis.
They think they are speaking English, but you are going to have a very difficult time understanding more than a word here and there.

-- Peter