Ajax associates with No Button doesn't work

Firstly, Thanks for a great plugin !

If i use the default theme, Everything is very ok. But i need to remove submit button.

I just try to hide submit button on this form so i used the Ajax fucntion(In FAQ they said button = 0 just applied for Ajax theme). Everything also Okay when i change to Ajax theme. But when I remove button (button parameter = 0) Our plugin broke..

My website is : (Widget named Search Form 1)

https://giayattom.com/san-pham/

I’m very appreciated if get help from this post. Thanks guys !