This is not a standard word that can be found in formal dictionaries.
It’s associated with the lingo of the Filipino gay community.
Frequently used on social media and in text messages, this term is short for the Tagalog phrase sa iyo (to you).
Lage ako nagme2ssage xeo.
= Lagi akong nagmemessage sa iyo.
= Lagi akong nagpapadala ng mensahe sa iyo.
= Lagi kitang pinapadalhan ng mensahe.
= I’m always messaging you.
= I’m always sending you messages.
= I always send a message to you.
More common spelling variation: sayo