what is means of this thai sentence?

ส่วนคำว่า อะไรอ่ะ จริงๆ ก็ผิด แต่ผมก็ใช้ เพราะไม่งั้นมันไม่ได้ feel ถือว่าเป็นภาษาแชตแล้วกัน
for "อะไรอ่ะ"this word,it is wrong.but i also use it.because not .............
so i have some thai word can not read means
can you tell me?
what is งั้น?
what is มัน?
what is ถือ?
what is แล้วกัน?

Thai people usually say the word "ไม่งั้น" when speaking in routine. Actually, this word has the same meaning as "ไม่อย่างนั้น or มิเช่นนั้น" which mean "otherwise" in English.

"มัน" = it 

"ถือว่า" = be regarded as

"แล้วกัน" = then

So the meaning of this sentence in English will be (as can be seen below)

For the word "อะไรอ่ะ" actually, it's not correct. But even I know it's wrong, I still use it. Otherwise, I'm not into its meaning. So "อะไรอ่ะ" is regarded as chat word then.

Hopefully, my correction can help you :)