Here’s a concise guide for flying Colombo (CMB) → Malaysia (typically Kuala Lumpur KUL, also Penang PEN on some airlines) when you need extra baggage — which airlines fly the route, how extra-baggage is sold, typical costs/limits, and practical steps to buy it.

Which airlines operate Colombo → Kuala Lumpur (direct)

• AirAsia (frequent low‑cost service). (AirAsia.com)
• SriLankan Airlines (multiple daily services, full-service carrier). (FlightsFrom.com)
• Malaysia Airlines (scheduled services). (FlightsFrom.com)

How extra baggage is normally handled (quick summary)

• Pre-purchase online (cheapest option in most cases): airlines let you buy extra kg or extra pieces during booking or later via “Manage booking” — usually at discounted rates versus airport prices. Pre-purchase is often allowed up to a few hours before departure. (srilankan.com)
• At the airport / check-in counter: allowed but typically more expensive per kg or per piece. (srilankan.com)
• Onboard/after security: not allowed — oversized/overweight items must be checked earlier. (Airline policy.)

Typical baggage models and fees (what to expect)

• SriLankan Airlines: uses a weight-based policy on many routes (you pay per kg for excess); they offer prepaid extra-baggage in blocks (e.g., 5 kg increments up to 50 kg), with online discounts versus airport rates. Per-piece limits usually 32 kg max per checked bag. You can buy prepaid baggage up to 3 hours before departure. (srilankan.com)
• AirAsia: low-cost model — free checked baggage is only included if you buy a bundle (Value Pack/Premium) or add checked allowance separately. Cabin baggage rules are strict (combined carry-on weight limits). Extra checked allowance is purchased as kg or by bag at booking/Manage Booking; buying in advance is cheaper. (AirAsia.com)
• Malaysia Airlines: offers standard free allowance depending on fare/class; extra pieces or overweight are charged (piece or kg rules can vary by fare/route). Pre-purchase via website/Manage Booking is recommended. (See airline site for exact rates for your fare/date.) (FlightsFrom.com)

How to buy extra baggage (recommended steps)

1. Check your ticket/fare: confirm your free checked allowance (kg or piece concept) on the e‑ticket or the airline website. (Allowances differ by fare class and airline.) (srilankan.com)
2. Pre-purchase via the airline website or Manage My Booking: this is almost always cheaper than airport rates and gives you time to repackage if a bag is overweight. SriLankan explicitly sells 5 kg blocks up to 50 kg online. (srilankan.com)
3. If booking on a low-cost carrier (AirAsia), add checked baggage or a bundled fare during booking; don’t rely on free baggage. (AirAsia.com)
4. If you must buy at the airport, arrive early — counter staff will weigh and charge per kg or per extra piece; expect higher fees. (srilankan.com)

Practical tips to save money / avoid surprises

• Pre-pay online as soon as you know your final weight — discounts often apply (SriLankan advertises up to 20% discount for pre-purchase in some blocks). (srilankan.com)
• Redistribute weight between checked and carry-on (subject to cabin allowance) to avoid overweight charges. Low-cost carriers have strict cabin weight/size limits. (AirAsia.com)
• Check maximum weight per piece (often 32 kg) and dimensions for special/sporting items. Some airlines charge a surcharge for overweight (23→32 kg) as a separate fee per bag. (srilankan.com)
• If you’re traveling on codeshare or mixed-carrier itineraries, baggage rules/fees may vary by operating carrier — verify the operating carrier’s policy. (srilankan.com)

If you’d like, I can:

• Check exact prices for extra baggage on specific flights/dates (I’ll need your travel dates and preferred airline), or
• Compare the cheapest total-fare + baggage combinations across SriLankan, AirAsia, and Malaysia Airlines for a date you give.

Which of the above would you like me to do next? (If you want me to look up fees now, tell me your departure date and whether you fly economy/business and which airport in Malaysia — KUL or PEN.)