Having a quick look at your code I see something that doesnt quite look right. In the loops to draw the tiles you are incrementing a in the innner y loop and b in the outer x loop but you are using them the other way around then using the Thle_Position_array. So if you swap the lines a=a+1 and b=b+1 over. You should also be reseting the b variable at the start of the y loop.
I think your code should be something like :
a=0
for x=0 to 1024 step 64
b=0
for y=0 to 768 step 64
bob = Tile_Position_Array(locationx +a,locationy +b)
drawimage tileset,x,y,bob
b=b+1
next
a=a+1
next
I think your code should be something like :
a=0
for x=0 to 1024 step 64
b=0
for y=0 to 768 step 64
bob = Tile_Position_Array(locationx +a,locationy +b)
drawimage tileset,x,y,bob
b=b+1
next
a=a+1
next