At present, you just can legally cross at four places to Myanmar:

• From Ranong (southern Thailand border) to Kawthaung (Burma Tanintharyi)
• From Mae Sai (northern Thailand border) to Tachilek (Burma Shan State)  
• From Ruili (China) to Mu Se (Burma Shan State)
• From Morei (India border) to Tamu (Burma Chin State)

You cannot reach Myanmar by land or by sea from Bangladesh, India and Laos.