"Message":"Invalid web service call, missing value for parameter: \u0027

Your service is accepting parameters named haha and tuan, but your JavaScript is passing in hahas and tuans. Remove the "s" from both:

data: JSON.stringify({ haha: $(this).val(),tuan: "hahaha" }),

Also, keep in mind that these parameters much match between client- and server-side with case-sensitivity.

Your JavaScript object property names must match the names of the parameters on the web service method so they can be bound appropriately. You currently have:

{ hahas: $(this).val(),tuans: "hahaha" }

which should probably be:

{ haha: $(this).val(), tuan: "hahaha" }