Thai Language dictation enable

On my hand is iPhone5s 16GB and run on iOS. 8.1.3

I'm enable dictation 3 language English, Japanese and Thai.

English and Japanese Dictation is very smooth

But Thai Dictation is super slow to automatically typing after I talked.

My native language is Thai because i am Thai.

After restored, it does work very smooth for 1-2 times but after that get worse again.

and every restoration it will work very well at the first and second time to enable and after that too long for waiting sometimes they can type in finally but sometimes no any typing.

What should i do ?

Buy new device or ignore it.

Best Regards,

K.Witoon