My GF currently has a Samsung J2 Mobile which is coming to its life’s end, she has mentioned about upgrading too a Samsung J6 at around 5000/6000 baht. For me it has many features she will never use, she only uses her phone for LINE, Facebook, You Tube and phone calls, is there a cheaper equivalent on the market to Samsung J6 ?

Yes, xiaomi Redmi and Huawei honor and vivo/oppo are budget focused sub brands with decent specs that can more than likely beat Samsung for performance /price ratio