Since you're postpaid and still in Canada, you can set all of this up in Self Serve before you fly out.
1. 30 Day Pass for a 42-day trip: the Easy Roam Travel Pass gives you unlimited talk & text and uses your plan's data for a fixed number of consecutive days, for one upfront charge. For the remaining ~12, you can either add a second pass or just let it run at the normal pay-per-use rate.
2. Adding a second pass while in Asia: Self Serve sometimes won't let you stack a second pass until the first one expires. When you get near the end of the 30 days, go to Self Serve → Mobile services → Manage add-ons and try removing/re-adding there. If it throws an error, that's the point to get a Koodo rep to add it for you. You can come back here to make a request.
3. 'I just want to receive a few calls' — do you even need a pass? Key thing to know: Easy Roam bills you whenever you actually use the phone abroad — answering a call, sending/receiving a text, or using data. Answering even one incoming call from Canada triggers the charge for that day. So for just a handful of calls, a full 30-day pass may be more than you need — without a pass, that same usage falls to pay-per-use rates instead. https://www.koodomobile.com/en/payperuse before you decide.
4. Receiving SMS/voicemail without Easy Roam: not having a pass (or turning off data roaming) only stops data — it doesn't make incoming calls or voicemail free. If you answer a call or tap to listen to a voicemail while overseas, it still triggers roaming charges. Classic gotcha: people tap the voicemail button abroad and get billed.
Bottom line: the 30 Day Pass is fine for the bulk of the trip if you'll be using the phone regularly; if it's genuinely just a few incoming calls, compare pay-per-use first.