Yoan Moncada isn't in the big leagues yet ... but he just spent $45k to make sure his swag is MAJOR ... turning his i8 BMW into a bona fide cool machine that freaking GLOWS IN THE DARK.
Moncada -- who signed a $31 million deal with the Red Sox last year -- wanted to roll to spring training in style ... so he took his ride down to customizing expert Alex Vega at The Auto Firm in Miami.
What did Alex and his Auto-Jedis do to the ride?
Vega tells us they took it apart "to the bone" and replaced the interior with custom Avorza leather, added Av30 forge wheels and repainted the car satin black with a glow in the dark metallic red.
Final price tag ... $45k.
Veteran move by the kid ... we all know the thots come out at night.