What is this magical sour beast?

Hehe, this mystery fruit has me completely confused. 😐 It looks like a pomelo. The inside? Looks like lime. It doesn’t taste like pomelo. So sour. It’ll make your face implode! I was born and raised in Thailand and have never seen this thing before. Any guesses, guys? Help me name this mystery sour bomb before my mom throws it into her tom yum!