The following appears on DL.com re mileage accrual, but it doesn't appear to address the Maximum Permitted Mileage issue.
Originally Posted by Delta
On connecting flights that require a change of plane and flight number, mileage credited will be calculated based upon the distance from origin to destination for each segment of the trip. However, use of connecting itineraries in lieu of nonstop and/or direct flights for the accumulation of additional mileage is not permitted. Delta reserves the right to limit mileage credit for an itinerary to the number of connecting flights actually traveled or the maximum number of segments shown in Delta's published schedule for a connection between any two cities, whichever is less.
This rule does not appear to apply to this situation, since DL doesn't not have any nonstop or direct flights LAX-BKK (yet-- after the NW merger, they might). And since this is an itinerary in the published schedule-- you can book it on DL.com-- it should be okay on the last part of the rule too. But the rule is strangely worded: it refers to limited mileage accrual to the number of permitted segments.
