To say that something is ON the TABLE, we say 在 TABLE 上 /zài TABLE shang/ 

To say that something is IN the ROOM, we say 在 ROOM 里 /zài ROOM li/ 

To say that something is UNDER the TABLE, we say 在 TABLE 下 /zài TABLE xia/ 

Instead of 上 /shang/,  下 /xia/, and 里 /li/ we can say 上面 /shàngmian/,  下面 /xiàmian/, and 里面 /lǐmiàn/