Does anyone please have knowledge of lock up garages to rent in Pattaya? 

Don't know of garages,  but you could rent a shop house,

some have been sitting vacant for years

for example here

https://www.google.com/maps/@12.9216092,100.8780428,3a,30.5y,338.74h,89.35t/data=!3m9!1e1!3m7!1s67FXwTFaAn2i3-bioy-NPQ!2e0!7i13312!8i6656!9m2!1b1!2i30?hl=en-TH